This invention relates generally to power generation systems and, more particularly, to combined cycle power plants that include large variable speed process equipment.
Some known integrated gasification combined cycle (IGCC) power plants use an air separation unit to generate a flow of oxidant for the gasification process. Generally, the air separation unit requires a source of relatively constant flow and pressure compressed air. A motor driven compressor is typically used for providing the compressed air at the necessary flow and pressure. However, the motor driven compressor is an expensive piece of equipment that uses significant electrical power. Furthermore, the motor driven compressor may be considered a parasitic load on the IGCC power plant, leading to a reduction in the overall efficiency.
Another source of air for the air processing unit is the compressor of the gas turbine associated with the IGCC power plant. However, the air provided by the compressor is at variable pressure and flows based on a load on the gas turbine.
For the foregoing reasons, there is a need for a system and method providing a source of relatively constant flow and pressure compressed air to an air processing unit. The system and method should not be a parasitic load on the IGCC power plant. The system and method should provide a source of relatively constant pressure and adjustable flow of compressed air across a load range of the gas turbine.